Actin Molecule

Q. Consider the given statements.
(a) The globular head of myosin acts as an ATPase enzyme.
(b) The G-actin polymerises to form F-actin in the presence of calcium ions.
(c) Troponin masks the active binding sites for myosin on actin filament.
Which of the above statements are true?

1. (a) and (c) only
2. (a), (b) and (c)
3. (a) and (b) only
4. (b) and (c) only

Q. White collagen fibres present in tendons are $\underset{–}{}$ and $\underset{–}{}$.
Select the correct option to fill in the blanks A and B respectively.
$\begin{array}{ccc}& \text{A}& \text{B}\\ \left(1\right)& \text{Branched}& \text{Elastic}\\ \left(2\right)& \text{Unbranched}& \text{Elastic}\\ \left(3\right)& \text{Branched}& \text{Inelastic}\\ \left(4\right)& \text{Unbranched}& \text{Inelastic}\end{array}$

Q. Which of the following is the function of troponin?

1. It helps in the fusion of actin and myosin
2. It covers myosin and prevents attachments of actin and myosin
3. It slides over myosin
4. It causes ${\mathrm{Ca}}^{+2}$ release

Q. Calcium receptive protein of muscles is

1. Myosin
2. Actin
3. Tropomyosin
4. Troponin

Q. During the resting state, the myosin binding sites on actin filaments are blocked by

1. none of these
2. tropomyosin
3. troponin-tropomyosin complex
4. troponin

Q.

Write trueor false. If false change the statement so that it is true.

(a) Actinis present in thin filament

(b) H-zoneof striated muscle fibre represents both thick and thin filaments.

(c) Humanskeleton has 206 bones.

(d) Thereare 11 pairs of ribs in man.

(e) Sternum is present on the ventralside of the body.

Q.

Label the parts and recognise the events 4 and 5

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(a) 4 (b) \( s \)

Q. The filaments of myofibril are made up of

1. Actin, troponin, tropomyosin
2. Actin, troponin
3. Actin, tropomyosin
4. Myosin, troponin

Q. Which one of the following pairs is NOT correctly matched?

1. Middle lamella – Layer between adjacent cell walls in plants derived from cell plates.
2. Plasmodesmata – The membrane surrounding the vacuole in plants.
3. Grana – Membrane bound discs in chloroplasts that contain chlorophylls and carotenoids.
4. Cristae – The tubular structure formed by the folding of the inner membrane of the mitochondrion.